He will return to the primary school in the new year and be known as Miss Lucy Meadows.

Nathan, 32, of Accrington, Lancs, is said to have told pupils at the Church of England school that he was born “with a girl’s brain in a boy’s body”.

A letter sent to children’s families said: “Mr Upton has made a significant change in his life and will be transitioning to live as a woman after Christmas.

“She will return to work as Miss Meadows.”

But angry parents say news of his sex change has left many children upset and confused.

Dad-of-three Wayne Cowie said: “I didn’t think I’d need the birds and the bees talk with my sons until they were at high school, and now they are coming home asking about transvestites. My lad is very confused and upset about it. He should have taken a couple of years off to sort himself out.”

One child, who is taught by Mr Upton, said: “It will feel very strange calling him Miss Meadows. He told us he was going to become a girl after Christmas.”

But one mother supported Mr Upton’s decision, saying: “I don’t see anything wrong with it. He’s not the first and he won’t be the last.”

In a statement Mr Upton said: “This has been a long and difficult journey for me and it was not an easy decision to make.”

Karen Hardman, headteacher of St Mary Magdalen’s Primary School, said she fully supported Mr Upton, adding: “This is a personal matter for our staff member who has our full support.

“We are all working together to ensure it has the least impact on the smooth running of the school.”